This invention is generally directed to the preparation of toner and developer compositions, and more specifically the present invention is directed to processes for obtaining toner compositions, including magnetic, single component, and colored toner compositions by flushing wherein, for example, water wetted magnetite is mixed with a polymer toner resin and solvent for the polymer thereby permitting effective dispersion of the magnetite and allowing the magnetite to be in contact with the toner resin. In one embodiment of the present invention, the toner compositions are prepared by surrounding the magnetite surface by flushing with a toner polymer resin to assure complete and intimate wetting of the magnetite by the polymer, and permanent association of the magnetite with the polymer. Thus, with the process of the present invention the magnetite is properly dispersed in the polymer selected, and the magnetite is in permanent contact with the polymer thereby, for example, avoiding undesirable toner depositions on the imaging member or photoconductor. Also, with the process of the present invention the toner compositions obtained when selected for electrophotographic, and especially xerographic imaging processes, substantially avoid the embedding of magnetite into the imaging member, which can cause undesirable comets to form thereon. Further, with the toner compositions prepared in accordance with the process of the present invention image defects in the final developer are avoided. Moreover, with the toner and developer compositions obtained by the processes of the present invention there is enabled a photoconductive imaging member present in an imaging apparatus to function for extended time periods, for example, up to 500,000 cycles while simultaneously preventing the localized accumulation of undesirable toner debris, and comets thereon which can encompass sufficient areas of the photoconductive members; and there is avoided unwanted toner spots on the final developed output copy, or such spots are minimized. Accordingly, there is permitted with the toner compositions obtained by the process of the present invention the elimination, or substantial reduction of undesirable comets and print deletions in electrophotographic imaging and printing devices, and the other advantages indicated herein.
There is disclosed in U.S. Pat. No. 4,601,918 a process for obtaining toner compositions by suspension polymerization wherein, for example, styrene and magnetite are mixed at a high shearing force and at a temperature of 50.degree. C., see Example I. Lauroyl peroxide is then added to the mixture and other components and the polymer resulting is washed and filtered. In U.S. Pat. No. 3,980,488, the disclosure of which is totally incorporated herein by reference, there is illustrated an improved process for conditioning colored organic pigments by partial communication of the crude pigment in an attrition, shear, or impact type mill followed by a further conditioning of the pigment by treating the partially milled pigment with a bleaching agent during a flushing operation to produce a pigmented organic vehicle having a pigment enhanced pigmentary quality, reference for example column 1. In column 2, lines 52, to column 3 of this patent it is indicated that it has been found that partially milled organic pigments can be flushed into an organic vehicle in the presence of a bleaching agent. The process of this patent is particularly described in column 2, line 60, to column 5. Other patents of interest include U.S. Pat. Nos. 4,218,530 and 4,273,848.
Moreover, toner and developer compositions containing charge enhancing additives, especially additives which impart a positive charge to the toner resin, and process for the preparation thereof are well know. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of certain quaternary ammonium salts as charge control agents for electrostatic toner compositions. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica. Further, there is illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer and toner compositions having incorporated therein as charge enhancing additives organic sulfate and sulfonate compositions; and in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions containing resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds, inclusive of cetyl pyridinium chloride. Generally, these toners are prepared by melt mixing followed by mechanical attrition, thus the magnetite if present is not flushed into the polymer; and with the prior art processes air pockets prevent the physical bonding of the magnetite to the toner polymer resin, a disadvantage avoided with the process of the present invention.
There is thus a need for processes for the preparation of toner compositions wherein there results no undesirable toner depositions on the imaging member incorporated into an electrographic imaging or printing apparatus. In addition, there is a need for toner and developer compositions that maintain their triboelectrical characteristics for extended time periods exceeding, for example, 500,000 developed images. Furthermore, there is a need for single component toners, and colored toners that possess many of the aforementioned characteristics. Also, there is a need for toner and developer compositions wherein the magnetite selected as a pigment is in constant contact with the toner polymer, and is permanently associated with the toner polymer preventing its release from said polymer. Also, there is a need for processes for toner compositions wherein the magnetite is properly dispersed therein.